Voltage and Electric Potential
THE HISTORY OF VOLTAGE AND ELECTRIC POTENTIAL In 1800, Alessandro Volta developed the voltaic pile, a counterpart to the battery, which produced a steady electric current. Volta had successfully determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. In the 1880s, the International Electrical Congress approved the volt for electromotive force. The volt was defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power. '' '' DEFINITION OF TERMS The electric potential is defined as the amount of "work" needed to move an electric charge from one point to the other. This shows the amount of work that is flowing from the first point to the second and how much it can perform. In the SI system of units, electrical potential is measured in volts, leading to the widely used term known as voltage or V. Named after Alessandro Volta, one volt is defined as one joule of energy per coulomb of charge. HOW IT ALL WORKS Electric Potential has an electric charge expended in a moving charged body from a reference point to any point in an electric field on work per unit. The complete potential of the reference point is zero, and the reference point itself is infinity. In a charged body the potential at a given point in a static electric field is independent the body of infinity to the given point. Potential is measured in volts and is sometimes called voltage. AN EXPERIMENT THAT CAN BE DONE The Experiment This experiment consists of modifying a circuit. You will need a battery, a wire, and a lightbulb. In this problem you will find the mathematical relationship between voltage (V), amperage (I). Step 1:You are given a circuit and any kind of battery.You will then adding resistors to the circuit. Step 2:Then turn on the switch a current will flow through the circuit. Make sure the resistance is at the right amount otherwise the lightbulb can explode. Step 3:Change the resistance to get the lightbulb to turn on. Once you get a working circuit write down your values, change the value of the battery, and try again. Step 4:Observe and take down notes Results You should begin to see the relationship between V, I, an d R. You should then be able to derive what the Amperage of the lightbulb is. If you know Ohm's law, you can apply it to a circuit where all values are known. By using different energy sources your results will differ. http://www.simplemotor.com/images/voltage.gif SOME USEFUL EQUATIONS The Wheel of Equations http://www.sengpielaudio.com/OhmschesGesetzA.gif How To Use Them 1. If the voltage across a 4-ohm resistor is 12 volts, the current through the resistor is? Solution: I=V/R I=12V/4-ohm I=3.0A 2. Wich combination of current and electromotive force would use energy at the greatest rate? (1) 10A at 110V (2) 8A at 110V (3) 3A at 220V (4) 5A at 110V Solution: The correct answer is 1, all you have to do is multiply A time V and see which answer will use enrgy at the fastest rate. In this case choice 1 would lead to the most. 3.What is the potential difference across a 10. ohm resistor which has 2.5 C per second running through it ? (1)0.25 V (2)4.0 V (3)25 V (4)250 V Solution:25 V 10-ohms(2.5C)= 25V SOME SHOCKING FACTS -In the United States, most homes use electrical power in the form of 120-volt, 60 Hz, single phase, alternating current. However, the voltage is not delivered at a constant 120-volts. -There are over 20 million cloud-to-ground lightning strikes detected per year in the 48 contiguous states of the U.S. -A stroke of lightning discharges from 10 to 100 million volts & 30000 amperes -You can generate about 3000 volts by walking on carpet REFERENCES http://encarta.msn.com/encyclopedia- Full of information on a wide range of topics http://www.reference.com/search?q=Voltage- A detailed explination of the process and uses of voltage Physics Reference Table- Contains all equations required for voltage and electric potential http://www.simplemotor.com/images/voltage.gif- Images of voltage in its everyday form http://www.nysedregents.org/testing/scire/regentphys.html- All the voltage problems you will ever need RESOURCES 1.Barrons Physics Review Book by Miriam A. Lazar - Many sample problems are included 2.Physics: Principles and Problems by Paul W. Zitzewitz The McGraw-Hill Companies, Inc. 1999 3."The World Book Encyclopedia." Chicago: World Book, Inc.,1992. 4.Gonick & Huffman The Cartoon Guide to Physics New York, NY: HarperCollins 1990 5.Regents Review Live- A T.V. show to help students with any questions they may have on a physics problem. resume writing services